Project Summary Many clinical and preclinical studies demonstrated that interferons (IFNs) exert a superior anti-tumor effect, when combined with retinoids, a class of vitamin-A metabolites. We identified a novel tumor suppressor Gene- associated with Retinoid-IFN induced Mortality-19 (GRIM-19) by a genome-wide knockdown strategy. In our recent publication in the PNAS, we have shown that GRIM-19 gene is either suppressed or mutated in several human cancers, including those of head and neck, and a mono-allelic loss of Grim-19 in mice enhances susceptibility to tumorigenesis. We demonstrated that direct administration of naked plasmids carrying GRIM-19 or lentiviruses expressing GRIM-19 into tumors robustly suppressed tumor growth and metastases, indicating its potential therapeutic utility. However, as a viable commercial strategy, we will recombinantly express GRIM-19 containing a protein transduction domain (PTD) to develop a potent protein therapeutic (rGRIM-19) that could block cancer cell growth. The PTD domain allows transfer of protein across the cell membrane. We already produced rGRIM-19 and purified. In our preliminary studies, rGRIM-19 kills oral cancer cells, but not normal cells. Based on our compelling preliminary data we hypothesize that rGRIM-19 will prove to be an effective biological therapeutic for controlling tumor growth. To test this hypothesis, we will investigate the therapeutic utility of rGRIM-19 for treating tumors in a relevant mouse model of head and neck squamous cell carcinoma (HNSCC). For this purpose, we have generated a conditional Grim- 19 KO mouse and also developed GRIM-19 deficient patient-derived xenograft (PDX) models. We will use the KO mice to generate oral tumors and determine if treatment of these tumors with rGRIM-19 would reverse the oncogenic gene signatures and enforce tumor growth suppression in vivo. A similar approach will be taken with the PDX models to study the effect of rGRIM-19 on human tumors in vivo. At the end of this study we expect to develop a protein therapeutic for treating human tumors.